The present invention relates to a method of joining elements in vehicle structures. More specifically, the present invention relates to a method of joining elements by casting around them as they are held in a desired configuration and to a node formed by such a method.
In many instances, it is necessary to create structural members such as frames to provide overall support to component devices. This is particularly true in the manufacture and assembly of vehicles such as automobiles, trucks, sport utility vehicles and the like. Such a vehicle frame is shown in U.S. Pat. No. 5,149,132 entitled SPLIT REAR TRUCK FRAME, which is assigned to the assignee of the present invention and is incorporated herein by reference. Another example of such a truck frame and its related mounting structures can be found in U.S. Pat. No. 5,308,115 entitled VEHICLE FRAME WITH OVERLAPPED SECTIONS, also assigned to the assignee of the present invention and incorporated herein by reference.
A vehicle is assembled, at least in part, by constructing a frame or main assembly and attaching subassemblies and components to the frame. The frame includes two generally parallel, spaced-apart side rail members which run substantially the length of the vehicle. Cross members span the distance between the side rails and are attached at their ends to the side rail members. Vehicle subassemblies and components include the engine cradle, suspension system, body panels, control arms, rear box load, cab, brake and fluid lines, and the like.
The unions or connections between elements are made directly or indirectly. Typically, direct unions are made by welding, bolting, riveting or the like. Indirect unions involve attaching a bracket to one member and then attaching a component to the bracket. Brackets are typically configured to accommodate a single particular component, and are typically attached by bolting, riveting, welding or the like.
Using bolting, riveting, and welding for these joints has a number of disadvantages. For example, one disadvantage with bolting, riveting, or welding involves the "fitting up" of the elements to be joined. That is, for a bolt or rivet to properly join two elements, the two elements must perfectly abut each other, or be fairly precisely parallel to one another. If one element is disposed at an angle to the element to which it is to be joined, the bolt or rivet will not be able to pull the two elements securely together. Therefore, careful orientation of the two elements is required to prepare the two elements for bolting, riveting, or welding.
Another disadvantage with bolting and riveting is that holes must be machined or stamped into the elements to accommodate bolts or rivets. This involves an additional manufacturing step, which increases the time, labor, and cost of the vehicle frame.
Bolting and riveting is further disadvantageous because the holes in the two elements to be joined must precisely match up. Therefore, tolerances for the placement of the holes must be fairly rigorously maintained. This increases the labor and therefore the cost of manufacturing the vehicle frame.
A still further disadvantage of bolting, riveting, and welding, involves the "stack up" of tolerances when multiple elements are joined. The elements must be designed to accommodate each other when mating features of each element, such as size and placement of holes for bolting, are at the extreme edges of their respective tolerance ranges. This is of particular concern when, for example, two elements are joined to one another and then joined to a third element. The third element must accommodate the stacked up tolerances or the sum of the tolerances of the first two elements.
A disadvantage to connecting elements through bracketry is that the brackets or mounting members are extra elements, requiring time and labor to produce and assemble. Further, additional parts require additional time and labor in regulating quality control and in tracking and storing inventory. This increases the cost of the resulting vehicle frame.
In light of the above-described disadvantages, it would be desirable to provide a method of joining or connecting elements that does not rely upon bolting, riveting, or welding. Further, it would be desirable to provide a joining method that eliminates the need for mating surfaces to match or "fit up" and to be precisely positioned for connection. Still further, it would be desirable to provide a connecting method that does not require specific structure, such as holes for bolting or riveting, to be incorporated into the elements to be joined. Further, it would be desirable to provide a method of uniting elements that would eliminate the stack-up of tolerances when multiple elements are joined.